Realizing an electronic device by packaging electronic components on a printed wiring board is known, for example. With such electronic devices, in cases where thermal runaway or dielectric breakdown occurs, large currents flow through a circuit and the electronic device is damaged. Thus, in order to protect an electronic device, providing a fuse unit on a printed wiring board as a failsafe function has been proposed.
A printed wiring board that internally includes a fuse unit has been proposed. Unexamined Japanese Utility Model Application (Registration) Publication No. H05-38937 discloses a printed wiring board equipped with a substrate, a pair of lands formed opposite each other on either side of an aperture unit provided on the substrate, a first trace pattern respectively coupled to the pair of lands, and a second trace pattern straddling the aperture unit to couple the pair lands and formed more finely than the first trace pattern. This printed wiring board of the related art described in Unexamined Japanese Utility Model Application (Registration) Publication No. H05-38937 is provided with a fine semiconductor pattern (the second trace pattern) over the aperture unit of the substrate.
Furthermore, Unexamined Japanese Patent Application KOKAI Publication No. H07-85771 discloses a printed wiring board having, on a film substrate, a fuse unit made up of metal foil and a pair of terminal units joined to the fuse unit. In this printed wiring board of the related art described in Unexamined Japanese Patent Application KOKAI Publication No. H07-85771, the fuse unit is encapsulated in resin (organic material) in order to reduce the effects of temperatures changes or other changes in ambient environment.
The contents of Unexamined Japanese Utility Model Application (Registration) Publication No. H05-38937 and Unexamined Japanese Patent Application KOKAI Publication No. H07-85771 are incorporated into this specification.